The present invention relates to the use of depolymerized apple and citrus fruit pectins as emulsifiers and emulsion stabilizers, particularly in the food sector.
Pectins are polysaccharides which have been studied for their structure, their chemical properties and their physical properties.
More precisely, pectins are galacturonic acid polymers which are linked in the .alpha.1-4 position and are esterified to a greater or lesser degree by methanol.
They have been described in detail, especially by Claus ROLIN in chapter 10, pp. 257-293, of the work entitled "Industrial Gums" 3rd edition, published by Roy L. Whistler and James N. Bemiller.
There are two distinct classes of pectins: pectins with a high degree of methylation, or "HM pectins", in which at least 50% of the galacturonic acid groups are esterified, and pectins with a low degree of methylation, or "LM pectins" in which fewer than 50% of the galacturonic acids are esterified. In some cases the secondary alcohol groups of the pectins can also carry acid groups, examples being acetyl groups or feruloyl groups. Neutral sugars can also be present on the polysaccharide chain; for example, rhamnose can be inserted in the chain whereas other sugars, such as arabinose, galactose or xylose, can be grafted on as side chains.
Pectins are generally extracted from the walls of plants and more particularly from citrus fruit rind and apple marc. The extraction process generally consists of:
1) an acid or basic treatment, which solubilizes the pectin; PA1 2) then a purification to separate the pectin in solution from the solid residues; PA1 3) and separation of the pectin from its solvent by precipitation with alcohol or by other methods of precipitation or water removal. PA1 acid hydrolysis treatment, PA1 ultrasound treatment, PA1 gamma ray treatment, PA1 mechanical degradation treatment by means of shear, PA1 .beta.-elimination treatment with an alkaline base, PA1 oxidative depolymerization using oxidizing reagents such as oxygen, chlorine, chlorite, hypochlorite, hydrogen peroxide, Fenton's reagent, etc., PA1 enzymatic or microbial degradation PA1 measurements of interfacial and surface tensions, PA1 measurements of the size of the oil globules, and PA1 application tests.
The extraction conditions are generally chosen for maximum preservation of the molecular weight of the pectins; a hydrolysis is thus generally carried out at temperatures varying from 50 to 99.degree. C. and at pH values varying from 1 to 3 for periods varying from a few minutes to several hours.
The molecular weight of the resulting pectins is generally greater than 80,000 daltons.
The physical properties of pectins are generally linked to their high molecular weight and their degree of methylation; pectins are thus gelling agents in more or less water-impoverished media and they combine with the casein in milk to stabilize the milk in acid media. Consequently there is a field of application centered around gelling in sugar-based media jams/marmalades, toppings, crystallized fruits, baking jams, etc.) and in milk-based media (custard tarts, sour milk drinks, etc.).
It has also been proposed to use pectins as emulsifiers (see Chemical Abstracts vol. 28, no. 2808, 1934, and vol. 64, no. 8855, 1966, and U.S. Pat. No. 1,759,182).
Among the pectins, those derived from sugarbeet are known to have good emulsifying and stabilizing properties at the same time.
Sugarbeet pectins differ from other pectins, especially citrus fruit or apple pectins, in that they contain a considerable number of acetyl groups, which inhibit the pectin gelling phenomenon.
On the other hand, the presence of these acetyl groups gives these pectins valuable surface-active properties, enabling them to be used as emulsifiers and emulsion stabilizers. In this connection, reference may be made to the article by I.C.M. DEA et al. in "Food Hydrocolloids", vol. 1, no. 1, pp. 71-88, 1986, and to the article by Nissim GARTI in "Food Structure", vol. 12, 1993, pp. 411-426.
EP-A1-0 426 434 also refers to the difference between sugarbeet pectins and other pectins and describes low molecular sugarbeet pectins which have emulsion stabilizing properties.